I, too, have had some concerns about running F@H w/o limit having some impact over the longterm. To put the odds most in my favor (lacking anything more substantial in the way of justifications), I DON'T:
-run it day-in/day-out
-run it aimlessly when ambient temperatures will be over 70 deg F
-run it w/o a surge suppressor on the AC.
In a sense, I tend to baby it.
I'll run it on F@H for 8-10 hrs a night, and only if there will be fresh, cool air filling the room (sub-70), such that the fan never kicks into high-speed mode. I'm not afraid to run it if the fan does kick into high while I am actively using it (playing games or watching a movie), but I don't make it run that way all day (or night), just to run F@H.
In the longterm, I hope this will translate into the optimal lifespan. Will it last for 10 yrs?...probably not. I would not expect such a complex piece to last that long w/o a mere hiccup (though, I would be pleased to be wrong). The model generation may be around for 10 yrs, but I don't expect a particular hardware to live that long. Especially, the optical drive- they simply have finite lifespans where it involves the laser diode and the actuator. This has been the case since the cd drive, imo, and I don't expect it to be different for a br drive.
While I never got to the point where I had to flip over my psx to get the disc drive to work, I did get about 7 yrs out of the dvd-drive in my ps2...had it since 2000 and it was able to play dvd movies up to around 2007, after which it was clearly showing signs of distress on being able to play a movie completely through w/o interruption. I'm fairly satisfied with how much life I got out of it (it still runs, actually, and never gave any problems playing actual ps2 games).